In order to check whether using our proposed two quasar selection criteria can avoid the color bias
in the SDSS quasar selection algorithm, we obtain a sample of 3089 FIRST radio selected SDSS-WISE quasars.
Because these radio-detected quasars are spectroscopically identified in SDSS without involving
the optical/infrared color selections, they are often adopted to check the quasar selection efficiency in using the proposed
selection criteria [1]}. In Figure 7 we demonstrate the results of using two quasar selection criteria.
From Figure 7 we can clearly see that with our \(z-W1/g-z\)  selection criterion, we can recover 3035 of the 3089
radio detected quasars at a completeness of 98.25%. This completeness raises to 98.63% for radio
quasars with \(z<4\) , which confirms the robustness of the \(z-W1/g-z\)  selection criterion.
With the W1-W2 selection criterion, we can recover 2989 of the 3089
radio detected quasars at a completeness of 96.76% and such completeness raises to 97.97% for radio
quasars with \(z<3.2\)  (note that the 'noise' at \(z>3.5\)  in Figure 7 is due to the small number statistics).
Our investigations demonstrate that the W1-W2 criterion and the \(z-W1/g-z\) 
criterion can be adopted to efficiently select \(z<3.2\)  and \(z<4\)  quasars respectively with very high
completeness. However, to selecte high redshift quasars with \(z>4\) , obviously we still
need to use other selection criteria (see [2]}, [3]}, [4]}).
